1. Field of the Invention
The present invention relates generally to an agricultural implement, including a work tool. More particularly, the present invention relates to an improved suspension system for agricultural implements having one or more floating work tools.
2. Background Art
Ground on which forage crops or other mowable foliage is grown is rarely smooth. Such ground essentially always varies in level both in a direction of travel of the mowing machine or harvester, and in a transverse or lateral direction.
Mowing machines having a variable height cutter have been available for decades. Mounted sickle mowers used in the mid-twentieth century could be raised and lowered using the tractor lift system. Towed mowers, by necessity, were made so the work tool could be raised and lowered, at least between an operating position and a transport position.
U.S. patent application Ser. No. 11/927,866 to Thompson et al. filed Oct. 30, 2007 is incorporated herein by reference in its entirety, relates to the field of this invention and is prior art to the instant application at this time.
In U.S. Pat. No. 6,250,055, a mower header suspension system is disclosed and is incorporated herein by reference. The suspension system comprises a pair of lower linkage arms and a single upper suspension arm. Provision for changes in ground elevation in the direction of travel is disclosed.
Disclosed in U.S. Pat. No. 6,055,800 is a mower header suspension system providing a variable header angle compared to the longitudinal direction and is incorporated herein by reference. The disclosed mechanism comprises two lower linkage arms and a single upper linkage arm.
The above described header suspension systems provide for changing the height of cut relative to the ground surface supporting the ground engaging wheels of the tractor or towed mower, but do not provide for a consistent cut height on ground that varies in level both in the direction of travel and in the lateral direction.
There is, therefore, a need for a method and apparatus for providing flexibility in header position to permit the header to raise and lower as ground elevation changes, and to rotate to adjust to lateral variations in ground surface levels.
There is an additional need for a header suspension system providing self-leveling, in the transverse direction, when the header is positioned in its transport mode.